Illustrative of the field of application of this invention are my prior U.S. Pat. Nos. 3,640,050, 4,820,254 and 5,211,619. Patents which have to do with producing bags of different widths are those using tucker mechanisms between sealing bars to force a greater amount of the bag between bars. These are the outward tuckers of U.S. Pat. Nos. 4,557,713 and 4,609,367 and the inward tuckers of U.S. Pat. No. 4,902,374. Tucking has drawbacks in web abuse, machine complexity and inducing tensions. Tucking during the clamping process also can produce slippage and distorted bag shapes.
According to the invention, a constant feed metering roll is employed in place of the prior art tuckers. This invention applies to both chain style sealing sections as well as drum style sealers. This results in the following benefits and advantages:
(1) allows constant web infeed velocity and tension, i.e., does not abuse the web with large tension variations, (2) reduced mechanical complexity, and (3) provides tension relief without extra motions or complexity.
More particularly, the apparatus for producing zipper closure bags from a continuous tube includes an elongated frame with means in the frame for advancing a continuous tube in a longitudinal path on the frame. The term "tube" as used herein can mean either a closed tube or a web folded on itself with an open longitudinally-extending side.
As indicated above, there is a metering roll rotatably mounted on the frame. Cooperating with the rotating metering roll is a nip roll rotatably mounted on the frame in contact with the metering roll and, for receiving the tube from the metering roll, I provide a sealing bar-equipped conveyor means movably mounted on the frame having a portion adjacent the metering roll.
The conveyor means is equipped with a plurality of equally spaced sealing bars extending in axial relation to the metering roll and the conveyor means has drive means synchronized with the metering roll rotating means. The metering roll itself has a plurality of circumferentially spaced, axially extending vacuum ports--with the port spacing corresponding to a desired bag width, and the sealing bars being spaced apart a distance no greater than the arcuate distance between adjacent ports whereby when successive segments of the tube are transferred from the metering roll to the sealing bars, a bag having a width greater than the sealing bar spacing will automatically buckle or drape between adjacent sealing bars.
As indicated previously, the invention is equally applicable to a straight chain or curved drum for carrying the sealing bars. It is also advantageous to provide the sealing bars in the conveyor means portion adjacent the metering roll with ports for applying vacuum to positively effect transfer of the tube from the metering roll to the conveyor.
Other advantages and objects of the invention may be seen in the ensuing specification.